Injury to internal tissue during surgery is followed by a healing process that frequently results in the attachment of adjacent tissues and organs by a fibrous mass, commonly referred to as adhesions. In essence it is a fibrous bridge that blocks the movement between two or more tissues that normally move freely, causing attendant pain. Post-surgical adhesions often occur following pelvic, abdominal and thoracic surgery, although there are many sites in the body where they occur from non-surgical intervention as well. Data have suggested that 67% to 93% of patients will develop adhesions following non-gynecologic abdominal surgery and 55% to 100% of patients will develop adhesions following gynecologic surgery. Despite refinement in operative technique and the recent introduction of products intended to minimize adhesion formation, the problem of postoperative adhesions remains a major cause of pain; and infertility after gynecologic surgery. Many of those patients who develop adhesions after gynecologic surgery may not experience any pain or discomfort from them, but it is impossible to predict which ones will have such problems, so it is important to minimize or eliminate adhesion problems in all such surgery.
All surgeons must deal with both the potential for adhesion formation after surgery, as well as the sequelae of adhesions from previous surgeries, which may markedly increase the difficulty of any particular surgical case. In addition to pelvic pain, abnormalities of bowel function, and small bowel obstruction can occur as a result of adhesions. Consider just gynecologic surgery, as a representative example. De novo or new adhesions may form at a site where none existed before, but where a surgical procedure was performed. Examples include a myomectomy incision for uterine fibroids or an ovarian incision at the time of ovarian cystectomy. De novo adhesions may also develop away from the site of surgery, such as adhesions developing around the tubes and ovaries at the time of a cesarean section. Adhesions may also reform following adhesiolysis or adhesiectomy.
Three general types of adhesions exist—filmy, vascular, and cohesive. The underlying pathology of all three, however, is similar. It is helpful to use the formation of peritoneal adhesions as the basis for understanding the underlying mechanism of the present invention, irrespective of where it is applied. The peritoneum is composed of multiple layers. The mesothelium is the innermost layer, a layer of connective tissue which contains the blood vessels, and a basement membrane. When the peritoneum (or other part of the body, including the skin) is injured (inevitable during surgery), there is an inflammatory response.
During the initial phase of this inflammatory response, inflammatory mediators and histamine are released from mast cells and leukocytes. Capillaries located within the connective tissue dilate and an increased permeability of the capillary wall is noted. This allows leukocytes, red blood cells and platelets to become concentrated at the site of in injury. A fibrinous exudate is thus formed at the site of injury. Multiple factors such as prostaglandins, lymphokines, bradykinin, serotonin, transforming growth factor and other chemotactic agents are present within the exudate material. It is generally understood that many of these factors trigger the activation of fibroblasts, the cells responsible for collagen, the fibrous protein which comprises the scaffold of adhesions. Without the replication of these fibroblasts, triggered by this inflammatory response, the production of collagen would not take place.
Before proceeding further, it is valuable to list additional areas where adhesions develop, whether from surgery or other aberrant physiological conditions. These include, among others:                Pleural adhesions from repeated thoracotomy to control the spread of cancer;        Pleural adhesions due to pulmonary tuberculosis;        Renal adhesions after renal surgery;        Pericardial adhesion following by-pass surgery;        Fallopian tube adhesions which develop after infection (e.g., genital tuberculosis);        Peritoneal adhesions associated with tuberculosis;        Peridural fibrosis following lumbar surgery (e.g., laminectomy);        Symblepharon (eyelid adhesions) from ocular burns, conjunctival infections (e.g., Chlamydia), Stevens-Johnson syndrome (allergic reaction to drugs e.g., bactrim);        Peritoneal adhesions resulting from radiotherapy to treat abdominal cavity cancer (e.g., colon, cervical, endometrial).        
When surgery is involved, there are four general approaches to adhesion reduction. These may generally be described as 1) minimizing injury during surgery, 2) reducing the local and inflammatory response, 3) inhibiting the coagulation cascade and promoting fibrinolysis, and 4) using barriers for separation of surfaces at high risk for adhesion formation. Regarding category 1) it is generally acknowledged that, even with the best techniques, the very nature of surgery involves the destruction of cells and the triggering of the inflammatory cascade. The Category 3) approach involves biochemical processes, quite different from both Categories 2) and 4). In Category 3) there are continuing, though not yet productive, efforts to interrupt and/or control the complex series of proteolytic events associated with activated platelets, their release of mediators that promote vesicle formation and platelet adherence, which then lead to enzyme activation, thrombin generation and associated fibrin formation. Before dealing with Category 2), which is the focus of this inventive disclosure, it is appropriate to make brief mention of the Category 4) approach, and its success. It should be noted, though, that use of physical barriers to suppress adhesion formation may be considered for only several of the circumstances listed above, where fibrous adhesions develop.
The barrier approach: To separate the surgically-incised tissue from adjacent tissues, by wrapping or coating the affected organ (generally) with a material that prevents contact of the fibrinous exudate from the injured tissue with adjacent tissues with which it might develop connective adhesions. There are limited areas where this approach has been effective, but such use has its attendant dangers as well. For example, Seprafilm® Adhesion Barrier is indicated for the reduction of post-surgical adhesions in patients undergoing abdominal or pelvic laparotomy. The type and frequency of adverse events reported are consistent with events typically seen following surgery when used as directed. Seprafilm should not be wrapped around an intestinal anastomosis as such usage may result in increased anastomotic leak-related events. Also achieving some success, in certain areas, have been Polyactive™, PRECLUDE Peritoneal Membrane™, Tissucol™ and INTERCEED(TC7)™. These are of a variety of compositions; for example, Seprafilm is a chemically modified sodium hyaluronate/carboxymethylcellulose fabric that is crosslinked with zinc, and is bioresorbable. INTERCEED(TC7) is a fabric composed of oxidized, regenerated cellulose that is also absorbed after a certain time period. PRECLUDE is a unique configuration of expanded polytetrafluoroethylene (ePTFE), Tissucol is a fibrin glue, and Polyactive is a degradable barrier, composed of a poly(ethyleneglycol) and poly(butyleneterephthalate) copolymer. All of these require manual placement in confined areas, with a significant level of dexterity, and all these physical systems have limitations in terms of where they may be used in the body, as well as demonstrating varying levels of success.
A more efficient way of contacting all the incised/eroded/or compromised tissues would be with a liquid infusion, where some component(s) of such infusion would have the capacity to interfere with the normal biochemical processes which otherwise result in the development of fibrous adhesions. A few such infusing solutions have been suggested: Ringer's lactate has been reported as effective, but a body of research indicates otherwise. Interperitoneal infusion studies of Lipiodol (an iodinated poppy seed oil) and methylene blue have been carried out in rats, and although “significant differences” in adhesion suppression were found between Lipiodol and control animals, none were found between methylene blue and control, nor between Lipiodol and methylene blue. The latter can be interpreted as indicating that the significance in the difference between Lipiodol and control was not that large, although mathematically still statistically valid.
The possibility of another type of liquid infusion with the potential for reducing the tendency for fibroblast replication arose from a publication by Kenyon et al., “Controlled wound repair in guinea pigs, using antimicrobials that alter fibroplasia” in Am J Vet Res. 1986 Jan; 47 (1):96-101. The publication is the result of work sponsored by one of the inventors (Kross) who at the time was the Director of Research at the Alcide Corp., a developer of oxychlorine (oxidizing) germicides. The latter were based on chlorous acid compositions which had, as one of its degradation products, the gaseous compound “Chlorine Dioxide” [ClO2].
A gelled chlorous acid composition was applied to a full-thickness incision in a rabbit's skin, which had been previous infected with a pathogenic organism. In addition to determining that there was full destruction of the infecting organism, it was noticed that the healed skin surface “. . . had a reduced level of scar formation. Microscopic evaluations indicated greatly reduced inflammatory infiltrates in Alcide—(i.e., chlorous acid)-treated wounds, indicating lack of fibroblast-stimulating activity by monocytes.” In reference to the Kenyon article, as noted in U.S. Pat. No. 5,622,725 (Kross), “irrigation of wounds with combined lactic acid and chlorite solutions significantly . . . promotes healing and epithelization by minimizing collagenous scar formation” (col. 11, lines 44-47). The present inventor continued to investigate these systems, and found that while the chlorous acid may have played a major role in that reduction, the acidity of the system was too low (e.g., pH≈3) to be physiologically compatible, particularly with internal tissues, and it was later learned that there are a number of stronger oxidants present, though transiently, in the chlorous acid degradation pathway to form ClO2, which are of significantly greater oxidative capacity (e.g., Cl2O2, HOCl, Cl2). It should be noted that the ClO2 that formed represented no more than about 5 to 10% of the end products of the chlorous acid disproportionation.
Continued investigation suggested, though, that ClO2 may itself have some beneficial properties at physiologically compatible pHs, and perhaps combine its known antimicrobial activity in wound environments with the possibility of minimizing adhesion and scar formation. This possibility was discussed in the '725 patent, which was primarily directed to the use of ClO2 in treating or preventing infections associated with peritoneal dialysis (specifically so-called Continuous Ambulatory Peritoneal Dialysis [CAPD]). The '725 patent describes using >125 to about 1000 ppm of ClO2 as a component of a peritoneal dialysis fluid, or in an aqueous solution for infusion into a peritoneal cavity wound in order to disinfect the wound and promote healing. No examples were provided which would support the contention that ClO2, per se is efficacious in minimizing or preventing fibrous adhesion formation. The evidence for the potential to minimize eventual adhesion formation was simply inferred from a series of comparative studies involving cell cultures of isolated polymorphonuclear leukocytes, “which are among the first cells to be found at a wound . . . ” (col. 13, line 54), with regard “to their response to a ClO2 solution.” The comparative agent was the known anti-inflammatory Ibuprofen.
The ClO2 in the treatment solution taught in the '725 patent was required to be present such that the “molar ratio of chlorine dioxide to any residual chlorite in the composition is at least 5:1 . . . ” (see claim 1, column 16, lines 8-10). In fact “(t)he chlorine dioxide solutions . . . have a relative molar ratio of chlorine dioxide to residual chlorite of at least 5:1, typically at least 7.5:1, and preferably at least 10:1.” (Col. 4, I. 31-34). Chlorite, according to the '725 patent, is to be minimized in the treatment solutions because of its detrimental effects. (See Col. 5, I. 48, 49: “. . . defined chlorine dioxide-to-chlorite molar ratios that limit tissue irritation . . . ”, and Col. 8, I. 46-50: “. . . in order to utilize the germ-killing and non-inflammatory qualities of chlorine dioxide, it is preferable to isolate it from chlorites . . . (which have detrimental cytotoxic effects).”
ClO2 generation, according to the '725 patent, was accomplished in either of three ways. All three involved the spontaneous degradation of chlorous acid (HClO2) by a so-called disproportionation mechanism. One technique involved the use of a strong acid combined with chlorite to form high levels of HClO2, which immediately degrades to ClO2 and several Cl-containing anions. The second involved the use of a moderate-strength acid, plus a triggering material such as chloride ion or certain sugars, leading to a lower yield of ClO2. The third technique involved contact of chlorite with heat-activated sugars, at an acidic pH, whereby ClO2 is formed in high levels. The '725 patent requires a minimum of 125 ppm of ClO2 to be effective in these peritoneal treatment applications, to a maximum concentration of 1000 ppm.
The present invention is the result of investigations to determine whether ClO2 solutions can indeed significantly suppress, or even prevent, the formation of fibrous adhesions in actual surgical procedures, in contrast to the suggested ability to lower the tendency for such activity by cell culture methods. There were no specific details, methods nor Examples provided in the '725 patent to validate this theoretical projection which was based on isolated cell cultures. It should be stressed that reduced scar [collagen] formation had only been observed by Kenyon et al. when freshly incised wounds to the skin had been treated with a chlorous acid composition, of which ClO2 was generated at a low percentage range (believed to be ≧0.01-0.02%).
However the present inventors were successful in demonstrating effective suppression of post-surgical adhesions in actual mammalian surgeries, by employing actually lower concentrations of mixed oxychlorine compositions, combining both ClO2 and chlorite ions, where the ClO2 itself was present at levels below 125 ppm; and the chlorite ion actually played a role in the activity. They also were successful in demonstrating that ClO2 in combination with hypochlorite and/or hypochlorous acid could be similarly effective at ClO2 levels below 125 ppm. Thereafter the inventors developed practical methods of optimizing the effects so as to bring such technology into operating theaters, and related environments.
It should be noted that in the '725 patent, the stipulated molar ratio of chlorine dioxide to chlorite ion, ClO2:ClO2−, was 5:1 at a minimum concentration of 125 ppm for the ClO2. This was dictated by the need for the solution to be non-irritating, as chlorite ion can be a tissue irritant at significant levels, while also being effective in the presence of significant organic matter, such as in the peritoneal cavity, in catheter biofilms, and in the dialysis fluids used for the CAPD treatment. ClO2, being an oxidant, is susceptible to reductive loss by reaction with many organic materials, particularly dextrose, which is the major solute in CAPD solutions. Our studies have shown that ClO2:ClO2− ratios of ≧5:1 are not only unnecessary, but contraindicated by the probable need for chlorite ion to enhance activity, as will be explained below. In addition, a level of ClO2 of 125 ppm, the lower level for the range claimed in the '725 patent [125 to 1000 ppm], represents the approximate maximum ClO2 concentration needed for ClO2 in the multicomponent oxychlorine system of the present invention to be effective in suppressing adhesions.
ClO2 is a gas that has a number of properties which militate against its usage at higher levels. One of these negative properties is ClO2's high inhalation toxicity. OSHA, the Occupational Safety and Health Administration of the US Department of Labor, allows only a 0.1 ppm ClO2 maximum level (i.e., 0.28 mg/m3) in the air of workers exposed to it for 8 hours, on a daily basis. Tied to this is the fact that ClO2 is a highly diffusive gas, and can permeate through virtually any plastic container in which it is contained. The higher the level in solution, the greater is the potential for diffusion to the surrounding air, and the concomitant potential for negatively affecting the respiratory capacity of both medical personnel and, more critically, the medically-compromised patients in the environment. For comparison, the corresponding allowable OSHA air maximum for chlorine (a noxious gas) is ten-times greater than for ClO2, namely 1 ppm. For short term contact of aqueous solutions of ClO2 with respect to surgical sites, the concern is less for the tissue involved than the quantities that could get into the air during application of a ClO2 solution, to reach and adversely affect the human lung.
There are three supplemental structures that are believed to play a role in the inventive method, and contribute to the activity of the multicomponent oxychlorine composition taught herein.